Hyaluronic acid-based gels including lidocaine

ABSTRACT

Disclosed herein are soft tissue fillers, for example, dermal and subdermal fillers, based on hyaluronic acids and pharmaceutically acceptable salts thereof. Some of the hyaluronic acid-based compositions can include a therapeutically effective amount of at least one anesthetic agent, for example, lidocaine. Compared to conventional compositions that include lidocaine, some of the hyaluronic acid-based compositions disclosed herein can have an enhanced stability, for example, when subjected to sterilization techniques or when stored for long periods of time. Methods and processes of preparing such compositions are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/186,451, filed on Nov. 9, 2018, which is a continuation of U.S.patent application Ser. No. 15/173,850, filed on Jun. 6, 2016, whichissued on Jun. 25, 2019, as U.S. Pat. No. 10,328,180, which is acontinuation of U.S. patent application Ser. No. 13/891,052, filed onMay 9, 2013, which issued on Jun. 7, 2016, as U.S. Pat. No. 9,358,322,which is a continuation of U.S. patent application Ser. No. 12/393,768,filed Feb. 26, 2009, which issued on May 28, 2013, as U.S. Pat. No.8,450,475, which claims the benefit of U.S. Provisional PatentApplication No. 61/085,956, filed Aug. 4, 2008, U.S. Provisional PatentApplication No. 61/087,934, filed on Aug. 11, 2008, and U.S. ProvisionalPatent Application No. 61/096,278 filed Sep. 11, 2008, the entiredisclosures all of which are incorporated herein by this specificreference.

FIELD OF THE INVENTION

The present invention generally relates to injectable soft tissuefillers and more specifically relates to hyaluronic acid-based dermaland subdermal fillers including an anesthetic agent.

BACKGROUND

It is generally accepted that as a person ages, the face begins to showeffects of gravity, sun-exposure, and years of facial muscle movement,such as smiling, frowning, chewing and squinting. The underlying tissuesthat keep the skin appearing youthful begin to break down, oftenresulting in laugh lines, smile lines, “crow's feet” and facial creasesoften referred to as the “effects of aging.”

In an effort to treat or correct the effects of aging, soft tissuefillers have been developed to help fill in facial lines and depressionsand for restoring fat loss-related tissue volume loss. The soft tissuefillers thereby temporarily restore a smoother, more youthfulappearance.

Ideally, soft tissue fillers are long-lasting, soft, smooth and naturalappearing when implanted in the skin or beneath the skin. Further, softtissue fillers are easy to implant into a patient using a fine gaugeneedle and require low extrusion force for injection. Ideal fillerswould also cause no adverse side effects, and would be injectable withminimal or no discomfort to the patient.

Collagen based soft tissue fillers were developed over 20 years ago, andfor some time, bovine collagen-based fillers were the only U.S. Food andDrug Administration (FDA)-approved dermal fillers. Because these dermalfillers are bovine based, one of the main disadvantages has been thepotential for allergic reaction in patients. It is believed thatapproximately 3-5% of human subjects show serious allergic reactions tobovine collagen, thus requiring careful testing before using thesefillers in any particular person. In addition to allergic reactions,collagen based fillers degrade rapidly upon injection and requirefrequent treatments to sustain a smoother, more youthful appearance.

In February 2003, human-derived collagen filler compositions receivedFDA approval. These collagens provide the advantage of a significantlyreduced risk of allergic reactions. However, despite the reducedincidence of allergic reactions, the human derived collagen fillersstill suffered from the rapid degradation of the injected product.

The search for fillers that do not provoke allergic reactions andsustain a smoother, more youthful appearance has brought about thedevelopment of hyaluronic acid (HA)-based products. In December 2003,the first HA-based filler was approved by the FDA. This was rapidlyfollowed by the development of other HA-based fillers.

HA, also known as hyaluronan, is a naturally occurring, water solublepolysaccharide, specifically a glycosaminoglycan, which is a majorcomponent of the extra-cellular matrix and is widely distributed inanimal tissues. HA has excellent biocompatibility and does not causeallergic reactions when implanted into a patient. In addition, HA hasthe ability to bind to large amounts of water, making it an excellentvolumizer of soft tissues.

The development of HA-based fillers which exhibit ideal in vivoproperties as well as ideal surgical usability has proven difficult. Forexample, HA-based fillers that exhibit desirable stability properties invivo, can be so highly viscous that injection through fine gauge needlesis difficult. Conversely, HA-based fillers that are relatively easilyinjected through fine gauge needles often have relatively inferiorstability properties in vivo.

One method to overcome this problem is to use crosslinked HA-basedfillers. Crosslinked HA is formed by reacting free HA with acrosslinking agent under suitable reaction conditions. Methods ofpreparing HA based soft tissue fillers including both crosslinked andfree HA are well known.

It has been proposed to incorporate certain therapeutic agents, forexample, anesthetic agents such as lidocaine, into injectable HA-basedcompositions. Unfortunately, HA-based injectable compositions whichincorporate lidocaine during the manufacturing process are prone topartial or almost complete degradation prior to injection, particularlyduring high temperature sterilization steps and/or when placed instorage for any significant length of time.

It is an objective of the HA-based soft filler compositions and methodsof making and using them as described herein to provide soft tissuefillers that do not cause allergic reactions in patients, arebiocompatible and are stable and usable in vivo and include one or morelocal anesthetic agents.

SUMMARY

The present description relates to soft tissue fillers, for example,dermal and subdermal fillers, based on hyaluronic acid (HA) andpharmaceutically acceptable salts of HA, for example, sodium hyaluronate(NaHA). HA-based compositions described herein include a therapeuticallyeffective amount of at least one anesthetic agent. In one embodiment,for example, the anesthetic agent is lidocaine. The present HA-basedcompositions including at least one anesthetic agent have an enhancedstability, relative to conventional HA-based compositions including, forexample, lidocaine, when subjected to sterilization techniques such asautoclaving, and/or when stored for long periods at ambient temperature.Methods for preparing such HA-based compositions are also provided aswell as products made by such methods.

Described herein are soft tissue filler compositions, said compositionsgenerally comprise: a hyaluronic acid (HA) component crosslinked with acrosslinking agent selected from the group consisting of 1,4-butanedioldiglycidyl ether (BDDE), 1,4-bis(2,3-epoxypropoxy)butane,1,4-bisglycidyloxybutane, 1,2-bis(2,3-epoxypropoxy)ethylene and1-(2,3-epoxypropyl)-2,3-epoxycyclohexane, and 1,4-butanediol diglycidylether; and at least one an anesthetic agent combined with thecrosslinked HA component.

In yet another embodiment, the at least one anesthetic agent islidocaine. In a further embodiment, the amount of the anesthetic agentis present at a concentration between about 0.1% and about 5.0% byweight of the composition. In still another embodiment, the anestheticagent is present at a concentration between about 0.2% and about 1.0% byweight of the composition. In one embodiment, the anesthetic agent islidocaine and is present at a concentration of about 0.3% by weight ofthe composition.

In still another embodiment, the soft tissue filler composition has anextrusion force of between about 10 N and about 13 N, for example, at arate of about 12.5 mm/minute. In yet another embodiment, the compositionhas a viscosity of between about 5 Pa·s and about 450 Pa·s, for example,when measured at about 5 Hz.

In one embodiment, the HA component is a gel, for example, a cohesive,hydrated gel. In one embodiment, the HA component is a crosslinked HAgel having no greater than about 1% to about 10% free HA. For purposesof this disclosure, free HA includes truly uncrosslinked HA as well aslightly crosslinked HA chains and fragments, all in soluble form inwater.

In yet other embodiments, the HA component comprises greater than about10%, for example, greater than about 15%, for example, up to or greaterthan about 20% free HA.

In yet another embodiment, the HA component is a gel comprisingparticles of crosslinked HA in a relatively fluidic medium of free HA.In some embodiments, the HA component has an average particle size ofgreater than about 200 μm, for example, greater than about 250 μm.

Further described herein is a soft tissue filler composition comprising:a HA component crosslinked with 1,4-butanediol diglycidyl ether (BDDE),said HA component having a degree of crosslinking of less than about 5%,for example, about 2%, and an anesthetic component having aconcentration between about 0.1% and about 5.0% by weight of the softtissue filler composition, wherein the anesthetic is lidocaine.

Further described herein are methods of preparing soft tissue fillercompositions, the methods comprising the steps of: providing a HAcomponent crosslinked with at least one crosslinking agent selected fromthe group consisting of 1,4-butanediol diglycidyl ether (BDDE),1,4-bis(2,3-epoxypropoxy)butane, 1,4-bisglycidyloxybutane,1,2-bis(2,3-epoxypropoxy)ethylene and1-(2,3-epoxypropyl)-2,3-epoxycyclohexane, and 1,4-butanediol diglycidylether or combinations thereof; adjusting the pH of said HA component toan adjusted pH above about 7.2; and adding a solution containing atleast one anesthetic agent to the HA component having the adjusted pH toobtain a HA-based filler composition.

In another embodiment, the composition is sterilized, for example, byautoclaving, to form a sterilized composition and wherein the sterilizedcomposition is stable at ambient temperature for at least about 6months, for example, at least 9 months, at least about 12 months ormore.

In still another embodiment, the adjusted pH is above about 7.5. Inanother embodiment, the method further comprises the step ofhomogenizing the HA component during or after the step of adding thesolution containing the at least one anesthetic agent. In a furtherembodiment, the step of homogenizing comprises subjecting thecomposition to mixing with a controlled shear.

In another embodiment, the step of providing a HA component comprisesproviding dry free NaHA material and hydrating the dry free NaHAmaterial in an alkaline solution to obtain an alkaline, free NaHA gel.In yet another embodiment, the alkaline, free NaHA gel has a pH greaterthan about 8.0. In still another embodiment the pH is greater than about10.

In a further embodiment, the HA component comprises greater than about20% free HA and the crosslinked portion of the HA component has a degreeof crosslinking of less than about 6% or less than about 5%.

In still a further embodiment, the soft tissue filler composition has aparticulate nature in that it comprises particles of crosslinked HAdispersed in a fluid soluble HA medium. In some embodiments, the averagesize of such particles is at least about 200 μm, and in otherembodiments the average size of such particles is at least about 250 μm.

Further described herein is a soft tissue filler composition comprising:a hyaluronic acid (HA) component crosslinked with 1,4-butanedioldiglycidyl ether (BDDE), said HA component having a degree ofcrosslinking of less than about 5%, and an anesthetic component having aconcentration between about 0.1% and about 5.0% by weight of the softtissue filler composition, wherein the anesthetic is lidocaine.

In a specific embodiment of the invention, a method of preparing a softtissue filler composition is further described, the method comprisingthe steps of: providing dry free NaHA material and hydrating the dryfree NaHA material in an alkaline solution to obtain an alkaline, freeNaHA gel; crosslinking the free NaHA gel with BDDE to form a crosslinkedalkaline HA composition with a degree of crosslinking less than about 5%and a pH above about 7.2; adding a solution containing 0.3% lidocaineHCl to the HA component having the adjusted pH to obtain said HA-basedfiller composition; homogenizing the HA-based filler composition therebyforming a homogenized HA-based filler composition; and sterilizing thehomogenized HA-based filler composition thereby forming a sterilizedHA-based filler composition, wherein the soft tissue filler compositionhas a particle size of greater than about 200 μm, for example, aparticle size of greater than about 250 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically illustrates the lidocaine concentration over time, ina gel tested in accordance with Example 4.

DEFINITIONS

Certain terms as used in the specification are intended to refer to thefollowing definitions, as detailed below. Where the definition of termsdeparts from the commonly used meaning of the term, applicant intends toutilize the definitions provided below, unless specifically indicated.

Autoclave stable or stable to autoclaving as used herein describes aproduct or composition that is resistant to degradation such that theproduct or composition maintains at least one, and preferably all, ofthe following aspects after effective autoclave sterilization:transparent appearance, pH, extrusion force and/or rheologicalcharacteristics, hyaluronic acid (HA) concentration, sterility,osmolarity, and lidocaine concentration.

High molecular weight HA as used herein describes a HA material having amolecular weight of at least about 1.0 million Daltons (mw≥10⁶ Da or 1MDa) to about 4.0 MDa. For example, the high molecular weight HA in thepresent compositions may have a molecular weight of about 2.0 MDa. Inanother example, the high molecular weight HA may have a molecularweight of about 2.8 MDa.

Low molecular weight HA as used herein describes a HA material having amolecular weight of less than about 1.0 MDa. Low molecular weight HA canhave a molecular weight of between about 200,000 Da (0.2 MDa) to lessthan about 1.0 MDa, for example, between about 300,000 Da (0.3 MDa) toabout 750,000 Da. (0.75 MDa).

Degree of Crosslinking as used herein refers to the intermolecularjunctions joining the individual HA polymer molecules, or monomerchains, into a permanent structure, or as disclosed herein the softtissue filler composition. Moreover, degree of crosslinking for purposesof the present disclosure is further defined as the percent weight ratioof the crosslinking agent to HA-monomeric units within the crosslinkedportion of the HA based composition. It is measured by the weight ratioof HA monomers to crosslinker (HA monomers: crosslinker).

Free HA as used herein refers to individual HA polymer molecules thatare not crosslinked to, or very lightly crosslinked to (very low degreeof crosslinking) the highly crosslinked (higher degree of crosslinking)macromolecular structure making up the soft tissue filler composition.Free HA generally remains water soluble. Free HA can alternatively bedefined as the “uncrosslinked,” or lightly crosslinked component of themacromolecular structure making up the soft tissue filler compositiondisclosed herein.

Cohesive as used herein is the ability of a HA-based composition toretain its shape and resist deformation. Cohesiveness is affected by,among other factors, the molecular weight ratio of the initial free HA,the degree of crosslinking, the amount of residual free HA followingcrosslinking, and HA-based composition pH. A cohesive HA-basedcomposition resists phase separation when tested according to the methoddisclosed in Example 1 herein.

DETAILED DESCRIPTION

The present disclosure generally relates to soft tissue fillers, forexample, dermal and subdermal fillers, based on hyaluronic acids (HA)and pharmaceutically acceptable salts of HA, for example, sodiumhyaluronate (NaHA). In one aspect, HA-based compositions describedherein include a therapeutically effective amount of at least oneanesthetic agent, for example, lidocaine. The present HA-basedcompositions including at least one anesthetic agent have an enhancedstability, relative to conventional HA-based compositions including, forexample, lidocaine, when subjected to high temperatures and pressures,for example, those experienced during heat and/or pressure sterilizationtechniques, for example, autoclaving, and/or for example, when stored atambient temperature for an extended period of time.

The stable compositions maintain at least one of, or all of, thefollowing aspects after effective autoclave sterilization and/orprolonged storage: transparent appearance, pH for use in a patient,extrusion force and/or rheological characteristics, HA concentration,sterility, osmolarity, and lidocaine concentration. Methods or processesof preparing such HA-based compositions are also provided as well asproducts made by such methods or processes.

As used herein, hyaluronic acid (HA) can refer to any of its hyaluronatesalts, and includes, but is not limited to, sodium hyaluronate (NaHA),potassium hyaluronate, magnesium hyaluronate, calcium hyaluronate, andcombinations thereof

Generally, the concentration of HA in the compositions described hereinis preferably at least 10 mg/mL and up to about 40 mg/mL. For example,the concentration of HA in some of the compositions is in a rangebetween about 20 mg/mL and about 30 mg/mL. Further, for example, in someembodiments, the compositions have a HA concentration of about 22 mg/mL,about 24 mg/mL, about 26 mg/mL, or about 28 mg/mL.

In addition, the concentration of one or more anesthetics is in anamount effective to mitigate pain experienced upon injection of thecomposition. The at least one local anesthetic can be selected from thegroup of ambucaine, amolanone, amylocaine, benoxinate, benzocaine,betoxycaine, biphenamine, bupivacaine, butacaine, butamben,butanilicaine, butethamine, butoxycaine, carticaine, chloroprocaine,cocaethylene, cocaine, cyclomethycaine, dibucaine, dimethisoquin,dimethocaine, diperodon, dycyclomine, ecgonidine, ecgonine, ethylchloride, etidocaine, beta-eucaine, euprocin, fenalcomine, fomocaine,hexylcaine, hydroxytetracaine, isobutyl p-aminobenzoate, leucinocainemesylate, levoxadrol, lidocaine, mepivacaine, meprylcaine,metabutoxycaine, methyl chloride, myrtecaine, naepaine, octocaine,orthocaine, oxethazaine, parethoxycaine, phenacaine, phenol,piperocaine, piridocaine, polidocanol, pramoxine, prilocaine, procaine,propanocaine, proparacaine, propipocaine, propoxycaine, pseudococaine,pyrrocaine, ropivacaine, salicyl alcohol, tetracaine, tolycaine,trimecaine, zolamine, and salts thereof. In one embodiment, the at leastone anesthetic agent is lidocaine, such as in the form of lidocaine HCl.The compositions described herein may have a lidocaine concentration ofbetween about 0.1% and about 5% by weight of the composition, forexample, about 0.2% to about 1.0% by weight of the composition. In oneembodiment, the composition has a lidocaine concentration of about 0.3%by weight (w/w %) of the composition. The concentration of lidocaine inthe compositions described herein can be therapeutically effectivemeaning the concentration is adequate to provide a therapeutic benefitwithout inflicting harm to the patient.

In one aspect of the invention, a method is provided for preparing aHA-based composition including an effective amount of lidocaine whereinthe method comprises providing a precursor composition furthercomprising a cohesive crosslinked HA-based gel, adding a solutioncontaining lidocaine, for example in the form of lidocaine HCl, theretoand homogenizing the mixture to obtain a cohesive, at least partiallycrosslinked, HA-based composition including lidocaine that is stable toautoclaving. The cohesive, crosslinked HA-based gel includes no greaterthan about 1% to about 10% of free or lightly crosslinked HA material byvolume (w/v %).

Without wishing to be bound by any particular theory of operability, itis believed that the high cohesivity of the precursor composition insome embodiments of the invention acts to substantially or entirelyprevent or impede any breakdown or degradation of the crosslinked HA inthe composition with the addition of lidocaine.

It is believed that such degradation may primarily occur because many,perhaps most crosslinked HA based gels are conventionally manufacturedin a manner that produces gels which are not sufficiently cohesive toprevent such degradation when lidocaine is added. It has now beendiscovered that the addition of lidocaine to sufficiently cohesivecrosslinked HA-based compositions does not cause substantial orsignificant degradation of the compositions, and the compositionsmaintain their integrity in terms of rheology, viscosity, appearance andother characteristics even when stored for a lengthy period of time, forexample, for a period of time of at least 6 months to a year or more,and even after being subjected to sterilization procedures, for example,autoclaving.

It is a surprising discovery that formulations of crosslinked HA-basedcompositions including lidocaine can be manufactured in a manner inaccordance with the invention to produce sterilization-stable,injectable HA/lidocaine compositions.

Further described herein is a method for preparing stable HA-basedcompositions containing an effective amount of lidocaine by preparing acohesive, crosslinked HA-based precursor composition, adding lidocainechlorhydrate to the precursor composition to form a HA/lidocaine gelmixture, and homogenizing the mixture, to obtain a crosslinked HA-basedcomposition that is stable to autoclaving.

In certain embodiments, the precursor composition is a gel whichincludes less than about 1% of soluble-liquid form or free HA. In otherembodiments, the precursor composition comprises no greater than about1% to about 10% of free HA by volume.

The precursor composition may comprise a first component includingrelatively highly crosslinked HA particles in a substantially solidphase, and a second component comprising free or relatively lesscrosslinked HA in a substantially fluidic phase in which the relativelyhighly crosslinked particles are dispersed. The composition can includeabout 10% to about 20% or greater of free HA by volume.

In some embodiments, the free HA makes up less than 20% by weight of thecomposition. For example, the free HA makes up less that 10% by weightof the HA component. In a further example, the second portion makes upbetween about 1% and about 10% by weight of the HA component.

For example, the precursor composition may comprise a cohesive, HA-basedgel.

In other embodiments, the free HA makes up greater than about 20% byweight of the HA component.

In some embodiments, the present compositions have a particulate natureand comprise particles of relatively highly crosslinked HA dispersed ina medium of relatively less crosslinked HA. In some embodiments, theaverage size of such particles of crosslinked HA is at least about 200μm or at least about 250 μm. Such particulate compositions are generallyless cohesive than otherwise similar compositions which have nodiscernable particles, or have particles having an average size of lessthan 200 μm.

For example, in some embodiments, the precursor composition may bemanufactured by pressing a mass of relatively highly crosslinkedHA-based gel through a sieve or a mesh to create relatively highlycrosslinked HA particles of generally uniform size and shape. Theseparticles are then mixed with a carrier material, for example, an amountof free HA to produce a gel.

Further, a method of preparing a HA-based composition including aneffective amount of lidocaine is provided wherein the method comprisesproviding a precursor composition including a substantially pH neutral,at least partially crosslinked HA-based gel and adjusting the pH of thegel to a pH of greater than about 7.2, for example, about 7.5 to about8.0. The method further comprises the step of combining a solutioncontaining lidocaine, for example in the form of lidocaine HCl, with theslightly alkaline gel after the pH has been so adjusted and obtaining aHA-based composition including lidocaine that is stable to autoclaving.

Another method of preparing a stable HA-based composition containing aneffective amount of lidocaine, as described elsewhere herein, generallycomprises the steps of: providing purified NaHA material, for example,in the form of fibers; hydrating the material; and crosslinking thehydrated material with a suitable crosslinking agent to form acrosslinked HA-based gel. The method further comprises the steps ofneutralizing and swelling the gel, and adding to the gel a solutioncontaining lidocaine, preferably an acidic salt of lidocainechlorhydrate, to form a HA/lidocaine gel. Further still, the methodfurther comprises homogenizing the HA/lidocaine gel and packaging thehomogenized HA/lidocaine gel, for example, in syringes for dispensing.The syringes are then sterilized by autoclaving at an effectivetemperature and pressure. In accordance with the present description,the packaged and sterilized cohesive NaHA/lidocaine gels exhibitenhanced stability relative to HA-based compositions including lidocainewhich are made using conventional methods.

The present products and compositions are considered to be sterile whenexposed to temperatures of at least about 120° C. to about 130° C.and/or pressures of at least about 12 pounds per square inch (PSI) toabout 20 PSI during autoclaving for a period of at least about 1 minuteto about 15 minutes.

The present products and compositions also remain stable when stored forlong periods of time at room temperature. Preferably, the presentcompositions remain stable for a period of at least about two months, orat least about six months, or at least about 9 months, or at least about12 months, or at least about 36 months, at temperatures of at leastabout 25° C. In a specific embodiment, the compositions are stable at atemperature up to about 45° C. for a period of at least two months.

The manufacturing process includes, in one embodiment, the initial stepof providing raw HA material in the form of dry HA fibers or powder. Theraw HA material may be HA, its salts and/or mixtures thereof. In apreferred embodiment, the HA material comprises fibers or powder ofNaHA, and even more preferably, bacterial-sourced NaHA. In some aspectsof the present description, the HA material may be animal derived. TheHA material may be a combination of raw materials including HA and atleast one other polysaccharide, for example, glycosaminoglycan (GAG).

In some embodiments, the HA material in the compositions nearly entirelycomprises or consists of high molecular weight HA. That is, nearly 100%of the HA material in the present compositions may be high molecularweight HA as defined above. In other embodiments, the HA material in thecompositions comprises a combination of relatively high molecular weightHA and relatively low molecular weight HA, as defined above.

The HA material of the compositions may comprise between about 5% toabout 95% high molecular weight HA with the balance of the HA materialincluding low molecular weight HA. In a typical embodiment of theinvention, the ratio of high molecular weight to low molecular weight HAis at least about, and preferably greater than 2 (w/w≥2) with the highmolecular weight HA having a molecular weight of above 1.0 MDa.

It will be appreciated by those of ordinary skill in the art that theselection of high and low molecular weight HA material and theirrelative percentages or ratios is dependent upon the desiredcharacteristics, for example, extrusion force, elastic modulus, viscousmodulus and phase angle expressed as the ratio of viscous modulus toelastic modulus, cohesivity, etc. of the final HA-based product. Foradditional information that may be helpful in understanding this andother aspects of the present disclosure, see Lebreton, U.S. PatentApplication Publication No. 2006/0194758, the entire disclosure of whichis incorporated herein by this reference.

The HA-based gels can be prepared according to the present descriptionby first cleaning and purifying dry or raw HA material having a desiredhigh/low molecular weight ratio. These steps generally involve hydratingthe dry HA fibers or powder in the desired high/low molecular weightratio, for example, using pure water, and filtering the material toremove large foreign matters and/or other impurities. The filtered,hydrated material is then dried and purified. The high and low molecularweight HA may be cleaned and purified separately, or may be mixedtogether, for example, in the desired ratio, just prior to crosslinking.

In one aspect of the present disclosure, pure, dry NaHA fibers arehydrated in an alkaline solution to produce an free NaHA alkaline gel.Any suitable alkaline solution may be used to hydrate the NaHA in thisstep, for example, but not limited to aqueous solutions containingsodium hydroxide (NaOH), potassium hydroxide (KOH), sodium bicarbonate(NaHCO₃), lithium hydroxide (LiOH), and the like. In another embodiment,the suitable alkaline solution is aqueous solutions containing NaOH. Theresulting alkaline gel will have a pH above 7.5. The pH of the resultingalkaline gel can have a pH greater than 9, or a pH greater than 10, or apH greater than 12, or a pH greater than 13.

The next step in the manufacturing process involves the step ofcrosslinking the hydrated, alkaline NaHA gel with a suitablecrosslinking agent. The crosslinking agent may be any agent known to besuitable for crosslinking polysaccharides and their derivatives viatheir hydroxyl groups. Suitable crosslinking agents include but are notlimited to, 1,4-butanediol diglycidyl ether (or1,4-bis(2,3-epoxypropoxy)butane or 1,4-bisglycidyloxybutane, all ofwhich are commonly known as BDDE), 1,2-bis(2,3-epoxypropoxy)ethylene and1-(2,3-epoxypropyl)-2,3-epoxycyclohexane. The use of more than onecrosslinking agent or a different crosslinking agent is not excludedfrom the scope of the present disclosure. In one aspect of the presentdisclosure, the HA gels described herein are crosslinked using BDDE.

The step of crosslinking may be carried out using any means known tothose of ordinary skill in the art. Those skilled in the art appreciatehow to optimize conditions of crosslinking according to the nature ofthe HA, and how to carry out crosslinking to an optimized degree.

Degree of crosslinking for purposes of the present disclosure is definedas the percent weight ratio of the crosslinking agent to HA-monomericunits within the crosslinked portion of the HA based composition. It ismeasured by the weight ratio of HA monomers to crosslinker (HAmonomers:crosslinker).

The degree of crosslinking in the HA component of the presentcompositions is at least about 2% and is up to about 20%.

In some embodiments, the degree of crosslinking is between about 4% toabout 12%. In some embodiments, the degree of crosslinking is less thanabout 6%, for example, is less than about 5%.

In other embodiments, the degree of crosslinking is greater than 5%, forexample, is about 6% to about 8%.

In some embodiments, the HA component is capable of absorbing at leastabout one time its weight in water. When neutralized and swollen, thecrosslinked HA component and water absorbed by the crosslinked HAcomponent is in a weight ratio of about 1:1. The resulting hydratedHA-based gels have a characteristic of being highly cohesive.

The HA-based gels in accordance with some embodiments of the inventionmay have sufficient cohesivity such that the gels will not undergosubstantial phase separation after centrifugation of the gel at 2000rd/min for 5 minutes. In another embodiment, the gels have thecharacteristic of being capable of absorbing at least one time theirweight of water and have sufficient cohesivity such that when swollenwith water at a gel/water weight ratio of about 1:1, the gels maintaintheir integrity, for example, when subjected to centrifugation.

The hydrated crosslinked, HA gels may be swollen to obtain the desiredcohesivity. This step can be accomplished by neutralizing thecrosslinked, hydrated HA gel, for example by adding an aqueous solutioncontaining of an acid, such as HCl. The gels are then swelled in aphosphate buffered saline (PBS) solution for a sufficient time and at alow temperature.

In one embodiment, the resulting swollen gels are highly cohesive withno visible distinct particles, for example, no visibly distinctparticles when viewed with the naked eye. In a preferred embodiment, thegels have no visibly distinct particles under a magnification of lessthan 35×.

The gels are now purified by conventional means such as, dialysis oralcohol precipitation, to recover the crosslinked material, to stabilizethe pH of the material and to remove any un-reacted crosslinking agent.Additional water or a slightly alkaline aqueous solution can be added tobring the concentration of the NaHA in the composition to a desiredconcentration.

The pH of the purified, substantially pH neutral, crosslinked HA gelsare preferably adjusted to cause the gel to become slightly alkalinesuch that the gels have a pH of greater than about 7.2, for example,about 7.5 to about 8.0. This step may be accomplished by any suitablemeans, for example, by adding a suitable amount of dilute NaOH, KOH,NaHCO₃ or LiOH, to the gels or any other alkaline molecule, solutionand/or buffering composition know by one skilled in the art.

An effective amount of lidocaine, such as lidocaine HCl, is then addedto the purified cohesive NaHA gels. For example, in some embodiments,the lidocaine HCl is provided in a powder form which is solubilizedusing water for injection (WFI). The gels are kept neutral with a bufferor by adjustment with diluted NaOH in order that the final HA/lidocainecomposition will have a desired, substantially neutral pH. Preferably,the final HA-based filler compositions including lidocaine will have alidocaine concentration of between at least about 0.1% and about 5%, forexample, about 2% by weight of the composition, or in another exampleabout 0.3%.

After the addition of the lidocaine HCl, or alternatively, during theaddition of the lidocaine HCl, the HA/lidocaine gels, or compositions,are homogenized to create highly homogenous cohesive HA/lidocaine gelshaving a desired consistency and stability. Preferably, thehomogenization step comprises mixing, stirring, or beating the gels witha controlled shearing force obtaining substantially homogenous mixtures.

The HA/lidocaine compositions described herein display a viscosity whichis dependent on the composition's properties and the presence of atleast one anesthetic agent. The viscosity of the HA/lidocainecomposition can be from about 50 Pa·s to about 450 Pa·s. In otherembodiments, the viscosity can be from about 50 Pa·s to about 300 Pa·s,from about 100 Pa·s to about 400 Pa·s, or about 250 Pa·s to about 400Pa·s, or about 50 Pa·s to about 250 Pa·s.

After homogenization, the HA/lidocaine compositions are introduced intosyringes and sterilized. Syringes useful according to the presentdescription include any syringe known in the art capable of deliveringviscous dermal filler compositions. The syringes generally have aninternal volume of about 0.4 mL to about 3 mL, more preferably betweenabout 0.5 mL and about 1.5 mL or between about 0.8 mL and about 2.5 mL.This internal volume is associated with an internal diameter of thesyringe which plays a key role in the extrusion force needed to injecthigh viscosity dermal filler compositions. The internal diameters aregenerally about 4 mm to about 9 mm, more preferably from about 4.5 mm toabout 6.5 mm or from about 4.5 mm to about 8.8 mm. Further, theextrusion force needed to deliver the HA/lidocaine compositions from thesyringe is dependent on the needle gauge. The gauges of needles usedgenerally include gauges between about 18G and about 40G, morepreferably about 25G to about 33G or from about 16G to about 25G. Aperson of ordinary skill in the art can determine the correct syringedimensions and needle gauge required to arrive at a particular extrusionforce requirement.

The extrusion forces displayed by the HA/lidocaine compositionsdescribed herein using the needle dimensions described above are at aninjection speeds that are comfortable to a patient. Comfortable to apatient is used to define a rate of injection that does not injure orcause excess pain to a patient upon injection to the soft tissue. Oneskilled in the art will appreciate that comfortable as used hereinincludes not only patient comfort, but also comfort and ability of thephysician or medical technician injecting the HA/lidocaine compositions.Although certain extrusion forces may be achievable with theHA/lidocaine compositions of the present description, one skilled in theart understands that high extrusion forces can lead to lack of controlduring injection and that such lack of control may result in additionalpain to the patient. Extrusion forces of the present HA/lidocainecompositions can be from about 8 N to about 15 N, or more preferablyfrom about 10 N to about 13 N, or about 11 N to about 12 N.

Sterilization, as used herein comprises any method known in the art toeffectively kill or eliminate transmissible agents, preferably withoutsubstantially altering of degrading the HA/lidocaine compositions.

One preferable method of sterilization of the filled syringes is byautoclave. Autoclaving can be accomplished by applying a mixture ofheat, pressure and moisture to a sample in need of sterilization. Manydifferent sterilization temperatures, pressures and cycle times can beused for this step. For example, the filled syringes may be sterilizedat a temperature of at least about 120° C. to about 130° C. or greater.Moisture may or may not be utilized. The pressure applied is in someembodiments depending on the temperature used in the sterilizationprocess. The sterilization cycle may be at least about 1 minute to about20 minutes or more.

Another method of sterilization incorporates the use of a gaseousspecies which is known to kill or eliminate transmissible agents.Preferably, ethylene oxide is used as the sterilization gas and is knownin the art to be useful in sterilizing medical devices and products.

A further method of sterilization incorporates the use of an irradiationsource which is known in the art to kill or eliminate transmissibleagents. A beam of irradiation is targeted at the syringe containing theHA/lidocaine solution, and the wavelength of energy kills or eliminatesthe unwanted transmissible agents. Preferable energy useful include, butis not limited to ultraviolet (UV) light, gamma irradiation, visiblelight, microwaves, or any other wavelength or band of wavelengths whichkills or eliminates the unwanted transmissible agents, preferablywithout substantially altering of degrading the HA/lidocainecomposition.

Further described are methods of manufacturing HA-based compositionsgenerally comprising the steps of providing a crosslinked HA-based gelwithout an anesthetic, (hereinafter, sometimes, a precursor gel)adjusting the pH of the precursor gel to obtain a gel having a pH ofbetween about 7.2 and 8.0, and adding a suitable amount of lidocaine, orother anesthetic agent, to the pH-adjusted gel to obtain a HA-basedcomposition that includes an anesthetic agent. In one embodiment, theprecursor gel is a highly cohesive gel comprising no greater than about10% free HA by volume. In another embodiment, the precursor gel is arelatively less cohesive gel comprising at least 10% to about 20% freeHA by volume.

EXAMPLE 1 Method for Testing for Cohesivity of Gel

The following tests may be performed in order to evidence cohesivity ofa HA-based gel composition for purposes of the present disclosure.

First, 0.2 g or 0.4 g of a gel composition to be tested is placed in aglass syringe. Next, 0.2 g or more of phosphate buffer is added to thesyringe and the mixture is thoroughly mixed for about 1 hour to obtain ahomogenous mixture. Then, the homogenized mixture is centrifuged for 5min at 2000 tr/min to remove the air bubbles and to allow thedecantation of any particles. The syringe is then held in a verticalposition and one drop of eosin colorant is deposited at the surface ofthe gel by means of a syringe and an 18G needle. After 10 min, the dyehas slowly diffused through the gel.

After dilution of the gel, homogenization and decantation, a relativelylow cohesivity gel shows a phase separation (an upper diluted lessviscous phase without particles and a lower one composed of decantedparticles that are visible with the naked eye or under microscope).Under the same conditions, a highly cohesive gel shows substantially nophase separation, and the dye is prevented from diffusing into thecohesive formulation. A relatively less cohesive gel, on the other hand,shows a clear phase separation.

EXAMPLE 2 Synthesis of a Soft Tissue Filler with Lidocaine

NaHA fibers or powder are hydrated in an alkaline solution, for example,an aqueous solution containing NaOH. The mixture is mixed at ambienttemperature, about 23° C., to form a substantially homogenous, alkalineHA gel.

A crosslinking agent, BDDE, is diluted in an aqueous solution and addedto the alkaline HA gel. The mixture is homogenized for several minutes.

Alternatively, BDDE can be added directly to the HA fibers (dry state)at the beginning of the process, prior to the hydration. Thecrosslinking reaction will then start relatively slowly at ambienttemperature, ensuring even better homogeneity and efficacy of thecrosslinking. See, for example, Piron et al., U.S. Pat. No. 6,921,819which is incorporated herein by reference in its entirety as if it werepart of the present specification.

The resulting crosslinked HA gel mixture is then heated at about 50° C.for about 2.5 hours. The material is now a highly crosslinked HA/BDDEgel (aspect=solid gel). This crosslinked gel is then neutralized with asuitable acidic solution. The neutralized HA gel is then swollen in aphosphate buffer at a cold temperature, for example a temperature ofabout 5° C., to obtain a highly cohesive HA gel. In this specificexample, the phosphate buffered saline solution containswater-for-injection (WFI), disodium hydrogen phosphate, and sodiumdihydrogen phosphate. When neutralized and swollen, the crosslinked HAcomponent and water absorbed by the crosslinked HA component is in aweight ratio of about 1:1.

The cohesive swollen HA gel is then mechanical stirred and filled intodialysis membranes and dialyzed against a phosphate buffer. The HA gelis filled into dialysis membranes and dialyzed against a phosphatebuffer for up to several days with regular changes of the bath, in orderto remove the un-reacted crosslinker, to stabilize the pH close toneutrality (pH=7.2) and to ensure proper osmolarity of the HA gel. Theosmolarity of the resulting cohesive HA gel is between about 200 mOsmoland about 400 mOsmol, most preferably about 300 mOsmol.

After dialysis, the resulting cohesive HA gel has a substantiallyneutral pH, preferably about 7.2, and no visibly distinct particles in afluidic media when viewed at a magnification of less than about 35×.

Lidocaine chlorhydrate (lidocaine HCl) in powder form is firstsolubilized in WFI and filtered through a 0.2 μm filter. Dilute NaOHsolution is added to the cohesive HA gel in order to reach a slightlybasic pH (for example, a pH of between about 7.5 and about 8). Thelidocaine HCl solution is then added to the slightly basic gel to reacha final desired concentration, for example, a concentration of about0.3% (w/w). The resulting pH of the HA/lidocaine mixture is then about 7and the HA concentration is about 24 mg/mL. Mechanical mixing isperformed in order to obtain a proper homogeneity in a standard reactorequipped with an appropriate blender mechanism.

If desired, a suitable amount of free HA gel may be added to theHA/lidocaine gel mixture with the advantage of increasing the kineticsof lidocaine delivery. For example, free HA fibers are swollen in aphosphate buffer solution, in order to obtain a homogeneous viscoelasticgel. This free HA gel is then added to the crosslinked HA/lidocaine gel(for example, at about 5%, w/w). The resulting gel is then filled intoReady-to-Fill sterile syringes and autoclaved at sufficient temperaturesand pressures for sterilization for at least about 1 minutes.

After autoclaving, the final HA/lidocaine product is packaged anddistributed to physicians. The product manufactured in accordance withthis method exhibits one or more characteristics of stability as definedelsewhere herein. For example, the autoclaved HA/lidocaine product has aviscosity, cohesivity, and extrusion force that are acceptable. Nodegradation of the HA/lidocaine gel product is found during testing ofthe product after the product has spent several months in storage.

EXAMPLE 3 Properties of Soft Tissue Fillers

Properties of HA/lidocaine compositions manufactured in accordance withmethods described herein are shown in the Table 1 below. Extrusion forcefor example was measured using an INSTRON® Advanced Materials TestingSystem Model 5564 (Instron, Norwood, Mass.) running BLUEHILL® softwareversion 2.11 (Instron, Norwood, Mass.).

TABLE 1 HA/lidocaine Composition Appearance Homogeneous transparent gelpH 7.2 Extrusion force (N) 10.8 N NaHA Content 23.7 mg/g SterilitySterile (SAL ≤ 10⁻⁶) Osmolarity 321 mOsml/kg Lidocaine Content (%) 0.29%2,6-dimethylaniline content Conforms

In order to ensure that product specifications were maintainedthroughout the shelf life of the composition, multiple studies wereperformed. In addition, 2,6 dimethylaniline content was measured inorder to confirm the absence of lidocaine degradation.

Table 2 provides a summary of stability testing results on thecomposition manufactured as described herein.

TABLE 2 HA/lidocaine Composition Test 3 month results 6 month results 9month results Aspect Transparent Conforms Conforms Conforms andhomogeneous pH 7.2 7.2 7.2 Extrusion Force (N) 11.9 11.1 11.9 NaHAConcentration 23.8 23.1 24.2 (mg/g) Sterility Conforms Conforms ConformsOsmolarity (mOsm/kg) 349 329 342 Lidocaine Content (%) 0.29 0.29 0.292,6-dimethylaniline Conforms Conforms Conforms content

It was discovered that at 9 months' time (from manufacture date), thecomposition continues to meet the product specifications.

EXAMPLE 4 Kinetic Release

The following example illustrates the kinetic of release of lidocainefrom cohesive HA gels according to the present description. The aim ofthe Example is to show that the lidocaine contained in HA gels accordingto the present description is freely released from the gels when placedin the skin.

Dialysis was performed for different periods of time (about 10 g of gelwere placed in a small dialysis bag and then put in 30g of water). Aftereach dialysis was stopped at a given time, the gel was homogenized witha spatula and the amount of lidocaine was determined by UV method. Thefinal concentration of the dialysis bath met the theoreticalconcentration of lidocaine which indicates the free release of lidocainefrom the gel.

Table 3 illustrates lidocaine concentration in % (w/w), correction ofthe value and determination of the % of released lidocaine.Additionally, FIG. 1 graphically illustrates the results tabulated inTable 3 below. Within FIG. 1 is indicated the theoretical equilibriumconcentration of lidocaine that would exist if the lidocaine wereretained in the gel or if it were to be freely released. As isgraphically illustrated therein, the data suggest that the lidocaine isfreely released from the gel.

TABLE 3 MMA4031- MMA4031- MMA4031- MMA4031- MMA4031- MMA4029- MMA3056EC6 EC2 EC3 EC4 EC5 EC7 Dialysis 0 hr 1 hr 30 5 hr 7 hr 23 hr 48 hr 72hr time (h) min [lidocaine] 0.29 0.20 0.16 0.15 0.08 0.07 0.07 (%)

FIG. 1 shows the concentration profile of lidocaine over time reaches anequilibrium that corresponds to free release of lidocaine. Theformulation of the composition in FIG. 1 is a cohesive crosslinked HAgel. The composition has a HA concentration of about 24 mg/mL, about 6%crosslinking, a G′ of about 170 and a high molecular weight to lowmolecular weight HA ratio from about 95% to 5% to about 100% highmolecular weight HA. This in vitro study shows that lidocaine is freelyreleased from the gel and not retained in the gel once implanted.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the present disclosurehas been made only by way of example, and that numerous changes in thecombination and arrangement of parts can be resorted to by those skilledin the art without departing from the scope of the invention, ashereinafter claimed.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques. Notwithstanding that the numerical ranges and parameterssetting forth the broad scope of the invention are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements.

The terms “a,” “an,” “the” and similar referents used in the context ofdescribing the invention (especially in the context of the followingclaims) are to be construed to cover both the singular and the plural,unless otherwise indicated herein or clearly contradicted by context.Recitation of ranges of values herein is merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention otherwise claimed. No languagein the specification should be construed as indicating any non-claimedelement essential to the practice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember may be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. It isanticipated that one or more members of a group may be included in, ordeleted from, a group for reasons of convenience and/or patentability.When any such inclusion or deletion occurs, the specification is deemedto contain the group as modified thus fulfilling the written descriptionof all Markush groups used in the appended claims.

Certain embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Ofcourse, variations on these described embodiments will become apparentto those of ordinary skill in the art upon reading the foregoingdescription. The inventor expects skilled artisans to employ suchvariations as appropriate, and the inventors intend for the invention tobe practiced otherwise than specifically described herein. Accordingly,this invention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Furthermore, numerous references have been made to patents and printedpublications throughout this specification. Each of the above-citedreferences and printed publications are individually incorporated hereinby reference in their entirety.

Specific embodiments disclosed herein may be further limited in theclaims using consisting of or and consisting essentially of language.When used in the claims, whether as filed or added per amendment, thetransition term “consisting of” excludes any element, step, oringredient not specified in the claims. The transition term “consistingessentially of” limits the scope of a claim to the specified materialsor steps and those that do not materially affect the basic and novelcharacteristic(s). Embodiments of the invention so claimed areinherently or expressly described and enabled herein.

In closing, it is to be understood that the embodiments of the inventiondisclosed herein are illustrative of the principles of the presentinvention. Other modifications that may be employed are within the scopeof the invention. Thus, by way of example, but not of limitation,alternative configurations of the present invention may be utilized inaccordance with the teachings herein. Accordingly, the present inventionis not limited to that precisely as shown and described.

What is claimed is:
 1. A soft tissue filler composition comprising: a mixture of soluble form hyaluronic acid (HA) present in the composition in an amount greater than about 10% by weight of the HA in the composition, particles of HA crosslinked with 1,4-butanediol diglycidyl ether (BDDE), and lidocaine in an amount effective to mitigate pain upon injection of the mixture, wherein the lidocaine is freely released in vivo.
 2. The soft tissue filler composition of claim 1, wherein the mixture has a HA concentration in a range between about 24 mg/mL and about 26 mg/mL.
 3. The soft tissue filler composition of claim 1, wherein the particles of HA crosslinked with BDDE are of about uniform size and shape.
 4. The soft tissue filler composition of claim 1, wherein the particles of HA crosslinked with BDDE have an average size of at least about 200 μm.
 5. The soft tissue filler composition of claim 1, wherein the lidocaine is present in the composition at a concentration of between about 0.1% and about 5% by weight of said composition.
 6. The soft tissue filler composition of claim 1, wherein the soft tissue filler composition is contained in a syringe.
 7. The soft tissue filler composition of claim 6, wherein the syringe has a needle gauge of between about 27 G and about 32 G.
 8. The soft tissue filler composition of claim 1, wherein the soft tissue filler composition is contained in a syringe having an internal volume of between about 0.5 mL and about 1.5 mL.
 9. The soft tissue filler composition of claim 1, wherein the soluble form HA and HA in the particles of HA crosslinked with BDDE are animal derived or bacterial- sourced.
 10. A soft tissue filler comprising: a hyaluronic acid (HA) component comprising HA crosslinked with 1,4-butanediol diglycidyl ether (BDDE) and uncrosslinked HA, wherein the uncrosslinked HA is present in the composition in an amount greater than about 10% by weight of the HA in the composition, wherein the crosslinked HA has a degree of crosslinking of about 2% to about 20%, and lidocaine in an amount effective to mitigate pain upon injection of the mixture, wherein the lidocaine is freely released in vivo.
 11. The soft tissue filler of claim 10, wherein the HA component of the soft tissue filler has a HA concentration of between about 20 mg/mL to about 30 mg/mL.
 12. The soft tissue filler of claim 10, wherein the HA component of the soft tissue filler comprises crosslinked HA particles that are of about uniform size and shape.
 13. The soft tissue filler of claim 12, wherein the crosslinked HA particles have an average size of at least about 200 μm.
 14. The soft tissue filler of claim 10, wherein the soft tissue filler is heat sterilized.
 15. A dermal filler comprising: particles of crosslinked HA in a fluidic medium of uncrosslinked HA, wherein the crosslinked HA is crosslinked with 1,4 butanediol diglycidyl ether (BDDE), and wherein the particles of crosslinked HA have a degree of crosslinking of less than about 6%; wherein the uncrosslinked HA is present in the composition in an amount greater than about 10% by weight of the HA in the composition, and lidocaine in an amount effective to mitigate pain upon injection of the dermal filler, wherein the lidocaine is freely released in vivo.
 16. The dermal filler of claim 15, wherein the particles of crosslinked HA are of about uniform size and shape.
 17. The dermal filler of claim 15, wherein the particles of crosslinked HA have an average size of at least about 200 μm.
 18. A method of preparing a hyaluronic acid (HA) based composition comprising: providing a hyaluronic acid (HA)-based gel crosslinked with 1,4-butanediol diglycidyl ether (BDDE); pressing the crosslinked HA-based gel through a mesh to produce crosslinked HA particles; mixing the crosslinked HA particles with a carrier material to produce the HA-based composition; wherein the carrier material comprises uncrosslinked HA present in an amount greater than about 10% by weight of the HA in the composition, adding lidocaine to the HA-based composition to form a HA/lidocaine gel mixture; and homogenizing the HA/lidocaine gel mixture, wherein the lidocaine is freely released in vivo from the composition prepared according to the method.
 19. The method of claim 18, further comprising sterilizing the HA-based composition.
 20. The method of claim 18, wherein the pressing step produces crosslinked HA particles of about uniform size and shape.
 21. The method of claim 18, wherein the mixing step produces the HA-based composition comprised of about 100% high molecular weight HA.
 22. The method of claim 18, wherein the hyaluronic acid (HA)-based gel crosslinked with BDDE is prepared by providing a NaHA material, hydrating the NaHA material in an alkaline solution to form a NaHA gel, and crosslinking the NaHA gel with BDDE.
 23. The method of claim 22, wherein the NaHA material is bacterial-sourced.
 24. The method of claim 18, further comprising introducing the HA-based composition into a syringe.
 25. The method of claim 18, wherein the syringe has a needle gauge of between about 27 G and about 32 G. 